The present invention relates generally to methods and apparatus for movement of equipment in passages, and more particularly, the present invention relates to drilling inclined and horizontally extending holes, such as an oil well.
The art of drilling vertical, inclined, and horizontal holes plays an important role in many industries such as the petroleum, mining, and communications industries. In the petroleum industry, for example, a typical oil well comprises a vertical borehole which is drilled by a rotary drill bit attached to the end of a drill string. The drill string is typically constructed of a series of connected links of drill pipe which extend between surface equipment and the drill bit. A drilling fluid, such as drilling mud, is pumped from the surface through the interior surface or flow channel of the drill string to the drill bit. The drilling fluid is used to cool and lubricate the drill bit, and remove debris and rock chips from the borehole created by the drilling process. The drilling fluid returns to the surface, carrying the cuttings and debris, through the space between the outer surface of the drill pipe and the inner surface of the borehole.
Conventional drilling often requires drilling numerous boreholes to recover oil, gas, and mineral deposits. For example, drilling for oil usually includes drilling a vertical borehole until the petroleum reservoir is reached. Oil is then pumped from the reservoir to the surface. As known in the industry, often a large number of vertical boreholes must be drilled within a small area to recover the oil within the reservoir. This requires a large investment of resources, equipment, and is very expensive. Additionally, the oil within the reservoir may be difficult to recover for several reasons. For instance, the size and shape of the oil formation, the depth at which the oil is located, and the location of the reservoir may make exploitation of the reservoir very difficult. Further, drilling for oil located under bodies of water, such as the North Sea, often presents greater difficulties.
In order to recover oil from these difficult to exploit reservoirs, it may be desirable to drill a borehole that is not vertically orientated. For example, the borehole may be initially drilled vertically downwardly to a predetermined depth and then drilled at an inclination to vertical to the desired target location. In other situations, it may be desirable to drill an inclined or horizontal borehole beginning at a selected depth. This allows the oil located in difficult-to-reach locations to be recovered. These boreholes with a horizontal component may also be used in a variety of circumstances such as coal exploration, the construction of pipelines, and the construction of communications lines.
While several methods of drilling are known in the art, two frequently used methods to drill vertical, inclined, and horizontal boreholes are generally known as rotary drilling and coiled tubing drilling. These types of drilling are frequently used in conjunction with drilling for oil. In rotary drilling, a drill string, consisting of a series of connected segments of drill pipe, is lowered from the surface using surface equipment such as a derrick and draw works. Attached to the lower end of the drill string is a bottom hole assembly. The bottom hole assembly typically includes a drill bit and may include other equipment known in the art such as drill collars, stabilizers, and heavy-weight pipe. The other end of the drill string is connected to a rotary table or top drive system located at the surface. The top drive system rotates the drill string, the bottom hole assembly, and the drill bit, allowing the rotating drill bit to penetrate into the formation. In a vertically drilled hole, the drill bit is forced into the formation by the weight of the drill string and the bottom hole assembly. The weight on the drill bit can be varied by controlling the amount of support provided by the derrick to the drill string. This allows, for example, drilling into different types of formations and controlling the rate at which the borehole is drilled.
The direction of the rotary drilled borehole can be gradually altered by using known equipment such as a downhole motor with an adjustable bent housing to create inclined and horizontal boreholes. Downhole motors with bent housings allow the surface operator to change drill bit orientation, for example, with pressure pulses from the surface pump. It will be understood that orientation includes inclination, asmuth, and depth components. Typical rates of change of orientation of the drill string are 1-3 degrees per 100 feet of vertical depth. Hence, over a distance of about 3,000 feet, the drill string orientation can change from vertical to horizontal relative to the surface. A gradual change in the direction of the rotary drilled hole is necessary so that the drill string can move within the borehole and the flow of drilling fluid to and from the drill bit is not disrupted.
Another type of known drilling is coiled tubing drilling. In coiled tubing drilling, the drill string tubing is fed into the borehole by an injector assembly. In this method the coiled tubing drill string has specially designed drill collars located proximate the drill bit that apply weight to the drill bit via gravity pull. In contrast to rotary drilling, the drill string is not rotated. Instead, a downhole motor provides rotation to the drill bit. Because the coiled tubing is not rotated or used to force the drill bit into the formation, the strength and stiffness of the coiled tubing is typically much less than that of the drill pipe used in comparable rotary drilling. Thus, the thickness of the coiled tubing is generally less than the drill pipe thickness used in rotary drilling, and the coiled tubing generally cannot withstand the same rotational and tension forces in comparison to the drill pipe used in rotary drilling.
A known method and apparatus for drilling laterally from a vertical well bore is disclosed in U.S. Pat. No. 4,365,676 issued to Boyadjieff, et al. The Boyadjieff patent discloses a pneumatically powered drilling unit which is housed in a specially designed carrier, and the carrier and drilling unit are lowered to a desired position within an existing vertical well bore. The carrier and drilling units are then pivoted into a horizontal position within the vertical well bore. This pivotal movement is triggered by a person located at the surface who pulls a string or cable that is attached to one end of the carrier unit. From this horizontal position, the drilling unit leaves the carrier unit and begins drilling laterally to create an abrupt switch from a vertical to a lateral hole. The carrier is removed from the well bore once the drilling unit exists the carrier unit.
The drilling unit disclosed in the Boyadjieff patent discharges air near the drill bit to push the cuttings and rock chips created by the drilling process around the drilling unit. These cuttings are supposed to fall into a sump located at the bottom of the vertical well bore. This causes the bottom end of the vertical well bore to be filled with debris and prevents the use of the vertical well bore. The debris ay also have a tendency to plug and fill the lateral hole. The drilling unit moves within the lateral hole by a series of teeth which are adapted to engage the sidewall of the lateral hole while the hole is being bored. These teeth transfer the drilling forces to the sidewalls of the hole to allow the drill bit to be pushed into the formation. The drilling unit is also connected to a cable guiding and withdrawal tool that is inserted into the vertical well bore to allow removal of the carrier and drilling unit from the lateral hole.
Another method and apparatus for forming lateral boreholes within an existing vertical shaft is disclosed in U.S. Pat. No. 5,425,429 issued to Thompson. The Thompson patent discloses a device that is lowered into a vertical shaft, braces itself against the sidewall of the vertical shaft, and applies a drilling force to penetrate the wall of the vertical shaft to form a laterally extending borehole. The device is generally cylindrical and includes a top section that is sealed to allow complete immersion in drilling mud. The top section also contains a turbine that is powered by the drilling mud. The bottom section of the device is open to the vertical shaft. The device is held in place within the vertical shaft by a series of anchor shoes that are forced by hydraulic pistons to engage the sidewall of the vertical shaft. These hydraulic pistons are powered by the turbine located in the top section of the device.
The device disclosed in the Thompson patent is anchored within the existing vertical shaft to provide support for the drilling unit as it drills laterally. The drilling unit uses an extendable insert ram to drill laterally into the surrounding formation. The insert ram consists of three concentric cylinders that are telescopically slidable relative to each other. The cylinders are hydraulically operated to extend and retract the insert ram within the lateral borehole. A supply of modular drill elements are cyclically inserted between the insert ram and the drill bit so that the insert ram can extend the drill bit into the surrounding formation. In operation, the drilling unit must be stopped and retracted each time the length of the insert ran is to be increased by inserting additional modular drill elements. The insert ram must then re-extend to the end of the lateral borehole to begin drilling again.
A further method for creating lateral bores is described in U.S. Pat. No. 5,010,965 issued to Schmelzer. The Schmelzer patent discloses a self-propelled ram boring machine for making earth bores. The system is operated using compressed air and is driven by a piston which triggers periodic blows by a striking tip.
U.S. Pat. No. 3,827,512 issued to Edmond discloses an apparatus for applying a force to a drill bit. The apparatus drives a striking bit, under hydraulic pressure, against a formation which causes the striking bit to form a borehole. In particular, the body of the apparatus is a cylinder containing two hydraulically operated pistons. Connected to the pistons are two anchoring assemblies which are located around the exterior surface of the tool. The anchoring assemblies contain a plurality of serrations and are periodically actuated to engage the sidewall of the borehole. These anchors provide support for the apparatus within the borehole such that a drill bit can be forced into the formation. The drill bit, however, can only be pushed in one direction. Additionally, the drill bit can only be periodically pushed into the formation because the apparatus must repeatedly unanchor and repressurize the piston chambers to move within the borehole.
The present invention provides improved methods and apparatus for movement of equipment in passages. In a preferred embodiment, the present invention provides improved methods and apparatus for moving drilling equipment in passages. More preferably, the present invention allows drilling equipment to be moved within inclined or completely horizontal boreholes that extend for distances beyond those previously known in the art. The equipment utilized for this purpose is structurally simple and provides for easy in-the-field maintenance. The structural simplicity of the present invention increases the reliability of the tool. The equipment is also easy to operate with lower initial and long-term costs than equipment known in the art. Additionally, the present invention is readily adapted to operate in environments where known methods and apparatuses are unable to function.
The apparatus is able to move a wide variety of types of equipment within a borehole, and in a preferred embodiment the present invention can solve many of the problems presented by prior art methods of drilling inclined and horizontal boreholes. For example, conventional rotary drilling methods and coiled tubing drilling methods are often ineffective or incapable of producing a horizontally drilled borehole or a borehole with a horizontal component because sufficient weight cannot be maintained on the drill bit. Weight on the drill bit is required to force the drill bit into the formation and keep the drill bit moving in the desired direction. For example, in rotary drilling of long inclined holes, the maximum force that can be generated by prior art systems is often limited by the ability to deliver weight to the drill bit. Rotary drilling of long inclined holes is limited by the resisting friction forces of the drill string against the borehole wall. For these reasons, among others, current horizontal rotary drilling technology limits the length of the horizontal components of boreholes to approximately 4,500 to 5,500 feet because weight cannot be maintained on the drill bit at greater distances.
Coiled tubing drilling also presents difficulties when drilling or moving equipment within extended horizontal or inclined holes. For example, as described above, there is the problem of maintaining sufficient weight on the drill bit. Additionally, the coiled tubing often buckles or fails because frequently too much force is applied to the tubing. For instance, a rotational force on the coiled tubing may cause the tubing to shear, while a compression force may cause the tubing to collapse. These constraints limit the depth and length of holes that can be drilled with existing coiled tubing drilling technology. Current practices limit the drilling of horizontally extending boreholes to approximately 1,000 feet horizontally.
The methods and preferred apparatus of the present invention solve these prior art problems by generally maintaining the drill string in tension and providing a generally constant force on the drill bit. The problem of tubing buckling experienced in conventional drilling methods is no longer a problem with the present invention because the tubing is pulled down the borehole rather than being forced into the borehole. Additionally, the current invention allows horizontal and inclined holes to be drilled for greater distances than by methods known in the art. The 500 to 1,500 foot limit for horizontal coiled tubing drilled boreholes is no longer a problem because the preferred apparatus of the present invention can force the drill bit into the formation with the desired amount of force, even in horizontal or inclined boreholes. In addition, the preferred apparatus allows faster, more consistent drilling of diverse formations because force can be constantly applied to the drill bit.
A preferred aspect of the present invention provides a method for propelling a tool having a body within a passage. The method includes causing a gripper including at least a gripper portion to assume a first position that engages an inner surface of the passage and limits relative movement of the gripper portion relative to the inner surface. The method also includes causing the gripper portion to assume a second position that permits substantially free relative movement between the gripper portion and the inner surface of the passage. The method further includes a propulsion assembly for selectively continuously moving the body with respect to the gripper portion while the gripper portion is in the first position.
Another preferred aspect of the present invention provides a method for propelling a tool having a generally cylindrical body within a passage. The method includes causing a first gripper portion to assume a first position that engages an inner surface of the borehole passage and limits relative movement of the first gripper portion relative to the inner surface. Simultaneously, a second gripper portion assumes a position that permits substantially free relative movement between the second gripper portion and the inner surface of the borehole. The body of the tool, consisting of a central coaxial cylinder and a valve control pack, moves within the borehole with respect to the first gripper portion. The first gripper portion then assumes a second position that permits substantially free relative movement between the first gripper portion and the inner surface of the passage, while the second gripper portion engages the inner surface of the borehole and limits relative movement of the second gripper portion relative to the inner surface. At this time the body of the tool moves relative to the second gripper portion. This process can be repeated to allow the body of the tool to selectively continuously move with respect to at least one gripper portion. While prior art methods prevent continuous movement and drilling within a borehole, the present invention allows continuous operation, and a force can be constantly maintained on the drill bit.
Another aspect of the present invention provides a method for propelling a tool having a generally cylindrical body within a passage. The method includes causing a first gripper portion to assume a first position that engages the inner surface of the borehole and limits relative movement of the first gripper portion relative to the inner surface of the borehole. The body of the tool is then moved with respect to the first gripper portion. The first gripper portion then assumes a second position that permits substantially free relative movement between the first gripper portion and the inner surface of the borehole. At this time a second gripper portion assumes a first position that engages an inner surface of the borehole and limits relative movement of the second gripper portion relative to the inner surface of the passage. The body of the tool is then moved with respect to the second gripper portion. The second gripper portion then assumes a second position that permits substantially free relative movement between the second gripper portion and the inner surface of the borehole. By selectively continuously moving the body with respect to at least one gripper portion when it is in the position that allows substantially free relative movement between the gripper portion and the inner surface of the borehole, the present invention can continuously move within the borehole.
Still another preferred aspect of the present invention provides a method of propelling a tool having a generally cylindrical body within a passage using first and second engagement bladders. The first engagement bladder is inflated to assume a position that engages an inner surface of the passage and limits relative movement of the first engagement bladder relative to the inner surface of the passage. An element of the tool then moves with respect to the first engagement bladder. The second engagement bladder is in a position allowing free relative movement between the second engagement bladder and the inner surface of the passage. The first engagement bladder then deflates, allowing free relative movement between the first engagement bladder and the inner surface of the passage. The second engagement bladder is then inflated to assume a position that engages an inner surface of the passage and limits relative movement of the second engagement bladder relative to the inner surface. At this time an element of the tool is moved with respect to the second engagement bladder. This process can be cyclicly repeated to allow the tool to generally continuously move forward within the passage.
In a further preferred aspect of the present invention, an ambient fluid is used to inflate the first and second engagement bladders. Preferably, the ambient fluid is drilling fluid or, more preferably, drilling mud. In this aspect of the invention, the drilling mud used to inflate the bladder is from the central flow channel of the drill string. When the engagement bladders are deflated, the drilling mud is preferably returned to the central flow channel. This is referred to as an open system.
In another preferred embodiment of the present invention, a fluid such as hydraulic fluid is used to inflate the engagement bladders. The hydraulic fluid may be stored within a reservoir within the tool or it may be pumped from the surface to the engagement bladders through a flow line. This is referred to as closed system.
Equipment known in the art for drilling horizontally extending boreholes is relatively bulky and expensive both in initial and long-term operating costs. These known devices also require lengthy maintenance time as in-the-field service is generally not a viable option. In contrast, the apparatus of the present invention reduces the cost and maintenance constraints of the known drilling methods. For example, the present invention is easy to operate, with lower initial and long-term costs than those known in the art. The present invention also eases in-the-field maintenance for several reasons. First, in this preferred embodiment, the apparatus of the present invention is designed to operate with ambient fluid. Preferably the ambient fluid is drilling fluid or, more preferably, drilling mud. Advantageously, when a fluid such as drilling mud is used to power the present invention, problems of contamination are eliminated. This design eases problems associated with deterioration of the tool caused by the mixing of different fluids. Alternatively, when a fluid such as hydraulic fluid is used to power the invention, the hydraulic fluid may be either stored within the body of the tool or pumped from the surface to the tool. Second, many of the parts of the present invention are easily removed and disconnected for in-the-field changes of various elements. These elements can simply be removed and replaced in-the-field, allowing quicker changeovers and continued operation of the tool. Significantly, this eliminates much of the down time of conventional drilling equipment.
Another preferred aspect of the present invention provides a method for propelling a tool having a generally cylindrical body within a passage. The method includes causing a gripper portion to assume a first position in which the gripper portion engages an inner surface of the passage and limits relative movement of the gripper portion relative to the inner surface of the passage. The gripper portion is also caused to assume a second position that allows substantially free relative movement between the gripper portion and the inner surface of the passage. A propulsion assembly is provided for selectively moving the body with respect to the gripper portion in the first position. The power source includes a piston having a head reciprocally mounted within a cylinder so as to define a first chamber on one side of the head and a second chamber on the other side of the head. The body of the tool is selectively moved with respect to the gripper portion by forcing fluid into the first or second chamber.
Yet another preferred aspect of the present invention provides a method for propelling a tool having a generally cylindrical body within a passage in which the movement of the tool is controlled from the surface. The surface controls can preferably be manually or automatically operated. The tool may be in communication with the surface by a line which allows information to be communicated from the surface to the tool. This line, for example, may be an electrical line (generally known as an xe2x80x9cE-linexe2x80x9d), an umbilical line, or the like. In addition, the tool may have an electrical connection on the forward and aft ends of the tool to allow electrical connection between devices located on either end of the tool. This electrical connection, for example, may allow connection of an E-line to a Measurement While Drilling (MWD) system located between the tool and the drill bit. Alternatively, the tool and the surface may be in communication by down linking in which a pressure pulse from the surface is transmitted through the drilling fluid within the fluid channel to a transceiver. The transceiver converts the pressure pulse to electrical signals which are used to control the tool. This aspect of the invention allows the tool to be linked to the surface, and allows Measurement While Drilling systems, for example, to be controlled from the surface. Additional elements known in the art may be linked to the various embodiments of the present invention.
In another preferred aspect, the apparatus may be equipped with directional control to allow the tool to move in forward and backward directions within the passage. This allows equipment to be placed in desired locations within the borehole, and eliminates the removal problems associated with known apparatuses. It will be appreciated that the tool in each of the preferred aspects may also be placed in an idle or stationary position with the passage. Further, it will be appreciated that the speed of the tool within the passage may be controlled. Preferably, the speed is controlled by the power delivered to the tool.
These preferred aspects of the present invention can be used, for example, in combination with drilling tools to drill new boreholes which extend at vertical, horizontal, or inclined angles. The present invention also may be used with existing boreholes, and the present invention can be used to drill inclined or horizontal boreholes of greater length than those known in the art. Advantageously, the tool can be used with conventional rotary drilling apparatuses or coiled tubing drilling apparatuses. The tool is also compatible with various drill bits, motors, MWD systems, downhole assemblies, pulling tools, lines and the like. The tool is also preferably configured with connectors which allow the tool to be easily attached or disconnected to the drill string and other related equipment. Significantly, the tool allows selectively continuous force to be applied to the drill bit, which increases the life and promotes better wear of the drill bit because there are no shocks or abrupt forces on the drill bit. This continuous force on the drill bit also allows for faster, more consistent drilling. It will be understood that the present invention can also be used with multiple types of drill bits and motors, allowing it to drill through different kinds of materials.
It will also be appreciated that two or more tools, in each of the preferred embodiments, may be connected in series. This may be used, for example, to move a greater distance within a passage, move heavier equipment within a passage, or provide a greater force on a drill bit. Additionally, this could allow a plurality of pieces of equipment to be moved simultaneously within a passage.
Advantageously, the present invention can be used to pull the drill string down the borehole. This advantageously eliminates many of the compression and rotational forces on the drill string, which cause known systems to fail. The invention is also relatively simple and eliminates many of the multiple parts required by the prior art apparatuses. Significantly, in one preferred aspect the tool is self-contained and can fit entirely within the borehole. Further, the gripping structures of the present invention do not damage the borehole walls as do the anchoring structures known in the art. For these and other reasons described in more detail below, the present invention is an improvement over known systems.
The present invention also makes drilling in various locations possible because, for example, oil reserves that are currently unreachable or uneconomical to develop using known methods and apparatuses can be reached by using an apparatus of the present invention to drill horizontal or inclined boreholes of extended length. This allows economically marginal oil and gas fields to be productively exploited. In short, the preferred embodiments of the present invention present substantial advantages over the apparatuses and methods disclosed in the prior art.